/*
 * @lc app=leetcode.cn id=61 lang=java
 *
 * [61] 旋转链表
 *
 * https://leetcode-cn.com/problems/rotate-list/description/
 *
 * algorithms
 * Medium (38.52%)
 * Likes:    122
 * Dislikes: 0
 * Total Accepted:    20.5K
 * Total Submissions: 52.9K
 * Testcase Example:  '[1,2,3,4,5]\n2'
 *
 * 给定一个链表，旋转链表，将链表每个节点向右移动 k 个位置，其中 k 是非负数。
 * 
 * 示例 1:
 * 
 * 输入: 1->2->3->4->5->NULL, k = 2
 * 输出: 4->5->1->2->3->NULL
 * 解释:
 * 向右旋转 1 步: 5->1->2->3->4->NULL
 * 向右旋转 2 步: 4->5->1->2->3->NULL
 * 
 * 
 * 示例 2:
 * 
 * 输入: 0->1->2->NULL, k = 4
 * 输出: 2->0->1->NULL
 * 解释:
 * 向右旋转 1 步: 2->0->1->NULL
 * 向右旋转 2 步: 1->2->0->NULL
 * 向右旋转 3 步: 0->1->2->NULL
 * 向右旋转 4 步: 2->0->1->NULL
 * 
 */
/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null || head.next == null || k == 0) {
            return head;
        }
        int l = 1;
        ListNode next = head.next;
        ListNode end = head;
        while (next != null) {
            l++;
            end = next;
            next = next.next;
        }

        k = k % l;
        if (k == 0) {
            return head;
        }

        ListNode newHead = head.next;
        ListNode newEnd = head;
        for (int i = 0; i < l - k - 1; i++) {
            newEnd = newHead;
            newHead = newHead.next;
        }
        newEnd.next = null;

        end.next = head;

        return newHead;
    }
}

